Performance Of Hybrid System Research Articles

A Review of Performance Hybrid Photovoltaic/Thermal System for General Applications

Photovoltaic modules can generate more electricity when receives a big quantity of solar radiation, but the efficiency of (PV) modules will drop when the temperature of solar cells is high. Therefore, reducing the high temperatures of (PV) modules will contribute to increase the electrical efficiency of (PV) modules by extraction the thermal energy associated with the PV modules and achieve an appropriate conversion efficiency of (PV). The aim of the study in this paper is to recognize the performance of hybrid (PV/T) systems in different places, conditions, module designs which can be used in household applications, hotels, etc. Aiming to supply of electricity and thermal energy. The study indicates to use of cooling technique (water or air) to cooling (PV) modules will contribute to a large extent to strengthen the work of solar cells and the efficiency of (PV/T) system as well. And the rate return of the system of electricity and thermal energy will increase, especially when the hybrid photovoltaic/thermal (PV/T) solar systems were properly designed and the conversion rate of absorbed solar radiation for (PV) modules will increase as well.

Improving Heat Transfer in Hybrid Solar Systems Using Liquid Metal Alloys as a Coolant

An improvement in performance of hybrid solar system with use of liquid metal alloy GaInSn as a coolant has been demonstrated in this study. The performance of hybrid system using GaInSn, water, and air as coolants under different operating conditions such as ambient temperature, different inlet velocities of fluid, solar irradiations is analyzed using simulation software ANSYS and the results obtained are validated using experiments. The results obtained from simulations and experiments are used for determining important performance criteria such as electrical efficiency, thermal efficiency, and exergy efficiency. The exergy, thermal, and electrical efficiencies were found to be at least 11%, 12%, and 12% higher for hybrid system using GaInSn as a coolant when compared to hybrid systems using air and water as coolants, respectively.

Analysis of a temperature dependent optical window for nanofluid-based spectral splitting in PV/T power generation applications

As an emerging technology, nanofluids can be used to split the solar spectrum for PV/T applications At present, most of the nanofluids developed for solar applications have been at low temperature, but it may be possible to develop fluids for high temperature systems. This study takes an in-depth look at the allowable temperature of the nanofluid and at how this directly affects the performance of hybrid system. In order to analyze this issue, the present work develops and experimentally validates a model to predict the performance of high temperature nanofluid-based spectral splitting PV/T systems for a wide range of optical properties, flow rates, and solar concentration ratios. The efficiency of system, the allowable temperature of fluid, and heat to electricity ratio are the main metrics of comparisons for this parametric analysis. It was found that the optimum ‘cut-on’ wavelength of nanofluid transparency should be set at 620–680nm for silicon solar cells, for concentration ratios of 10–50, when the allowable temperature of nanofluid is 400°C. This value will then move towards longer wavelengths as the allowable temperature of the nanofluid increases. The ‘cut-off’ wavelength for nanofluid transparency should be the bang-gap of the cell, or 1100nm in the case of silicon cells. When an optically ideal nanofluid is adopted, it was found that the power generated in the proposed hybrid system will come mainly from the thermodynamic conversion process. Therefore, we can conclude from a technical perspective that nanofluid-based PV/T systems should focus on developing fluids with as high as possible allowable temperature ratings.

Instruction-throughput regulation in computer processors with data-center applications

This paper tests a recently-proposed technique for regulating output performance of Discrete Event Dynamic Systems and Stochastic Hybrid Systems. The controller is based on an integrator with a variable gain, adjusted so as to guarantee wide stability margins of the closed-loop system. The gain is adjusted by estimating, in real time, the derivative of the plant function via approximations to its IPA derivative. The technique is robust to computational errors in the loop, and hence these approximations are designed for fast computation rather than precision. The development of the regulation technique has been motivated by applications in computer processors, and extensively tested in the past on a cycle-level, full system simulator. In this paper we describe implementations of the regulator on an Intel machine based on the Haswell processor, and apply it to control the instructions’ throughput of various industry program-benchmarks as well as data-center applications.

Application of cascading thermoelectric generator and cooler for waste heat recovery from solid oxide fuel cells

Besides electricity generation, solid oxide fuel cells (SOFCs) produce a significant amount of waste heat, which needs to be immediately removed to ensure the normal operation of SOFCs. If the waste heat is recovered through bottoming thermal devices, the global efficiency of SOFCs can be improved. In this study, a new hybrid system mainly consisting of a thermoelectric generator, a thermoelectric cooler and an SOFC is proposed to recover the waste heat from SOFC for performance enhancement. The thermodynamic and electrochemical irreversible losses in each component are fully considered. An analytical relationship between the SOFC operating current density and the thermoelectric devices dimensionless electric current is derived, from which the range of SOFC operating current density that permits the thermoelectric devices to effectively work is determined. The equivalent power output and efficiency for the hybrid system are specified under different operating current density regions. The feasibility and effectiveness are illustrated by comparing the proposed hybrid system with the stand-alone SOFC. It is found that the power density and efficiency of the proposed system allow 2.3% and 4.6% larger than that of the stand-alone SOFC, respectively. Finally, various parametric analyses are performed to discuss the effects of some design and operation parameters on the hybrid system performance.

Performance comparison investigation on solar photovoltaic-thermoelectric generation and solar photovoltaic-thermoelectric cooling hybrid systems under different conditions

ABSTRACTThe performance of solar photovoltaic-thermoelectric generation hybrid system (PV-TGS) and solar photovoltaic-thermoelectric cooling hybrid system (PV-TCS) under different conditions were theoretically analysed and compared. To test the practicality of these two hybrid systems, the performance of stand-alone PV system was also studied. The results show that PV-TGS and PV-TCS in most cases will result in the system with a better performance than stand-alone PV system. The advantage of PV-TGS is emphasised in total output power and conversion efficiency which is even poorer in PV-TCS than that in stand-alone PV system at the ambient wind speed uw being below 3 m/s. However, PV-TCS has obvious advantage on lowering the temperature of PV cell. There is an obvious increase in tendency on the performance of PV-TGS and PV-TCS when the cooling capacity of two hybrid systems varies from around 0.06 to 0.3 W/K. And it is also proved that not just a-Si in PV-TGS can produce a better performance than the stand-alone PV system alone at most cases.

Thermodynamic assessment of SOFC-ICGT hybrid cycle: Energy analysis and entropy generation minimization

Hybrid power systems are being developed by the integration of fuel cell with conventional gas turbine. Integration of solid oxide fuel cell (SOFC) with gas turbine (GT) to form a hybrid cycle based power plant has been considered as this is known to be highly efficient primarily performance of SOFC being not limited to Carnot efficiency. In this article, a novel and optimal thermal integration of SOFC with intercooled-recuperated gas turbine has been presented. The novel contribution of this work is integration of blade cooled gas turbine model to a SOFC model. 1st and 2nd law thermodynamic analysis has been performed analyzing the influence of compression ratio (rp,c) and turbine inlet temperature (TIT) on hybrid plant specific work, hybrid efficiency, blade coolant requirement and entropy generation rate. The performance of hybrid system has been optimized by entropy generation minimization, for this purpose a constraint based algorithm has been developed, which is a function of recirculation ratio, mass of fuel and TIT, based on which gas composition at the anode exit stream has been examined. It has observed that the entropy generation first increases and then decreases as TIT increases. Furthermore, a unique performance contour has also been plotted for proposed hybrid cycle, which can be utilized by power plant designer. At TIT 1800K and rp,c 20, optimal efficiency has been achieved with entropy minimization of 8.05 W/K.

Cycle analysis of solid oxide fuel cell-gas turbine hybrid systems integrated ethanol steam reformer: Energy management

A solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system that uses such liquid fuels as ethanol is attractive for distributed power generation for applications in remote rural areas or as an auxiliary power unit. The SOFC system includes units that require and generate heat; thus, its energy management is important to improve its efficiency. In this study, a SOFC-GT integrated system with the external steam reforming of ethanol to produce hydrogen for the SOFC is proposed. Two SOFC-GT hybrid systems using a high-temperature heat exchanger and cathode exhaust gas recirculation are considered under isothermal conditions. The effects of key operating parameters, such as pressure, fuel use and turbomachinery efficiency, on the SOFC-GT hybrid system performance are discussed. The simulation results indicate that recycling the cathode exhaust gas from the SOFC-GT system requires less fresh air from the compressor, to maintain the SOFC stack temperature, and the heat recovered from the SOFC system is sufficient to supply both the fuel processor and air pre-heater. In contrast, an external heat is needed for the SOFC-GT system coupled to a recuperative heat exchanger.

Performance of a novel baffled osmotic membrane bioreactor-microfiltration hybrid system under continuous operation for simultaneous nutrient removal and mitigation of brine discharge

The present study investigated the performance of an integrated osmotic and microfiltration membrane bioreactor system for wastewater treatment employing baffles in the reactor. Thus, this reactor design enables both aerobic and anoxic processes in an attempt to reduce the process footprint and energy costs associated with continuous aeration. The process performance was evaluated in terms of water flux, salinity build up in the bioreactor, organic and nutrient removal and microbial activity using synthetic reverse osmosis (RO) brine as draw solution (DS). The incorporation of MF membrane was effective in maintaining a reasonable salinity level (612–1434mg/L) in the reactor which resulted in a much lower flux decline (i.e. 11.48–6.98LMH) as compared to previous studies. The stable operation of the osmotic membrane bioreactor–forward osmosis (OMBR-FO) process resulted in an effective removal of both organic matter (97.84%) and nutrient (phosphate 87.36% and total nitrogen 94.28%), respectively.

Exergy and energy analysis of photovoltaic-thermoelectric hybrid systems

In this paper, a one-dimensional model is proposed for analyzing the features of photovoltaic-thermoelectric (PV-TE) hybrid systems based on the thermodynamic laws. The system contains a photovoltaic solar cell and a thermoelectric module. The hybrid systems convert concentrated sunlight into electric power by the PV cell and then utilize the rest thermal energy by the TE module. The effects of the concentration ratio and the PV cells technology used on the performance of the PV-TE hybrid systems are discussed. Based on the first law of thermodynamics, the energy analysis is used to evaluate the output performance of the hybrid system. And the output electric power of the hybrid system is calculated. Moreover, the second law of thermodynamics is applied to the exergy analysis of the hybrid system. The exergy losses caused by the irreversible process of solar radiation converted into electric power and thermal energy are evaluated. The calculation results demonstrate that high concentration ratio and suitable PV cell used in the PV-TE hybrid system can promote the system output efficiency.

Experimental analysis of hybrid and conventional air conditioning systems working in hot-humid climate

This paper reports the experimental performance characteristics of a hybrid air conditioning system consists of a conventional (vapor compression) system integrated with thin-multilayer activated alumina bed with single, double and triple-layers. The performance characteristics of both systems are investigated under hot very humid climate with fresh air mixing ratio from 40 to 100% that is replicated at various process air temperature (28–36°C) and relative humidity (50–80%). The performance characteristics of hybrid and conventional evaporators and systems are compared under different conditions. Also, effect of desiccant cycle duration on hybrid system performance is investigated. The obtained results revealed that thin-multilayer alumina bed has substantial effect on hybrid system characteristics. Using the right desiccant layers, hybrid systems achieve better characteristics (smaller evaporator size system and compressor power with higher COP) than conventional system for all the mixing ratios. In the case of pure fresh air, the degree of superheat, pressure ratio and compressor power are lower than those for conventional system by 14.5, 2.0 and 2.7% with higher COP of hybrid system by 12.4%. Short cycle duration has higher sensible heat factor and lower evaporator size while long cycle duration has lower compressor power and higher COP.

A cost-emission model for fuel cell/PV/battery hybrid energy system in the presence of demand response program: ε-constraint method and fuzzy satisfying approach

Optimal operation of hybrid energy systems is a big challenge in power systems. Nowadays, in addition to the optimum performance of energy systems, their pollution issue has been a hot topic between researchers. In this paper, a multi-objective model is proposed for economic and environmental operation of a battery/fuel cell/photovoltaic (PV) hybrid energy system in the presence of demand response program (DRP). In the proposed paper, the first objective function is minimization of total cost of hybrid energy system. The second objective function is minimization of total CO2 emission which is in conflict with the first objective function. So, a multi-objective optimization model is presented to model the hybrid system’s optimal and environmental performance problem with considering DRP. The proposed multi-objective model is solved by ε-constraint method and then fuzzy satisfying technique is employed to select the best possible solution. Also, positive effects of DRP on the economic and environmental performance of hybrid system are analyzed. A mixed-integer linear program is used to simulate the proposed model and the obtained results are compared with weighted sum approach to show the effectiveness of proposed method.

Open Loop and Closed Loop Performance of Solid Oxide Fuel Cell Turbine Hybrid Systems During Fuel Composition Changes

The dynamic behavior of a solid oxide fuel cell gas turbine hybrid system (SOFC/GT) from both open and closed loop transients in response to sudden changes in fuel composition was experimentally investigated. A pilot-scale (200–700 kW) hybrid facility available at the U.S. Department of Energy, National Energy Technology Laboratory was used to perform the experiments using a combination of numerical models and actual equipment. In the open loop configuration, the turbine speed was driven by the thermal effluent fed into the gas turbine system, where the thermal effluent was determined by the feedforward fuel cell control system. However, in the closed loop configuration, a load-based speed control system was used to maintain the turbine speed constant at 40,500 rpm by adjusting the load on the turbine, in addition to the implementation of the fuel cell system control. The open loop transient response showed that the impacts of fuel composition changes on key process variables, such as fuel cell thermal effluent, turbine speed, and cathode feed stream conditions, in the SOFC/GT systems were propagated over the course of the test, except for the cathode inlet temperature. The trajectories of the aforementioned variables are discussed in this paper to better understand the resulting mitigation/propagation behaviors. This will help lead to the development of novel control strategies to mitigate the negative impacts experienced during fuel composition transients of SOFC/GT systems.

Experimental study on hybrid solar system fitted with special heat exchanger and flat reflectors

The hybrid photovoltaic/thermal (PV/T) solar water systems are not cost economic because of low concentration ratios, less combined efficiencies and non-standardisation of heat exchanger surfaces. The simple and effective technique used to increase performance of hybrid system must enhance available solar radiation on its surface for its working period. This can be accomplished by fitting flat reflectors to module side. This paper analyses performance of spiral flow heat exchanger of hybrid system with reflectors fixed to shorter sides of module. The results such as performance efficiencies of photovoltaic, thermal, and combined photovoltaic/thermal are compared for forced and natural circulation of water through heat exchanger of system. At peak PV point, natural flow system worked with combined efficiency of 56.60% and forced flow system worked with marginally high combined efficiency of 57.74%. The results of the study showed that for this system, thermo-siphon method if used can be an ideal solution for generation of electrical power and hot water.

Experimental study on hybrid solar system fitted with special heat exchanger and flat reflectors

The hybrid photovoltaic/thermal (PV/T) solar water systems are not cost economic because of low concentration ratios, less combined efficiencies and non-standardisation of heat exchanger surfaces. The simple and effective technique used to increase performance of hybrid system must enhance available solar radiation on its surface for its working period. This can be accomplished by fitting flat reflectors to module side. This paper analyses performance of spiral flow heat exchanger of hybrid system with reflectors fixed to shorter sides of module. The results such as performance efficiencies of photovoltaic, thermal, and combined photovoltaic/thermal are compared for forced and natural circulation of water through heat exchanger of system. At peak PV point, natural flow system worked with combined efficiency of 56.60% and forced flow system worked with marginally high combined efficiency of 57.74%. The results of the study showed that for this system, thermo-siphon method if used can be an ideal solution for generation of electrical power and hot water.

A controller model for integration of hybrid energy system into the grid

This paper introduces a controller model for the integration, of a wind system and photovoltaic system into the utility grid. The problem of integration of hybrid renewable energy based hybrid renewable energy generation system is that it relies heavily on weather conditions, PV and wind air speed. So, there is a necessity for developing control techniques for grid integration for such hybrid system, including a method for voltage and current control that stabilises the voltage and current. A PID control is developed in this work that is suitable for hybrid renewable energy system. Then, the system behaviour and performance are studied. For different weather conditions and fault condition systems, stability is also considered when there are change weather conditions in PV and air speed or a fault in the system. This paper advocates that the proposed PID controller gives a good performance. In this paper, solar energy is hybrid with wind energy. The developed MATLAB/SIMULINK design improves for integration of hybrid system performance and the results are presented.

Analysis of the Primary Constraint Conditions of an Efficient Photovoltaic-Thermoelectric Hybrid System

Electrical efficiency can be increased by combining photovoltaic (PV) and the thermoelectric (TE) systems. However, a simple and cursory combination is unsuitable because the negative impact of temperature on PV may be greater than its positive impact on TE. This study analyzed the primary constraint conditions based on the hybrid system model consisting of a PV and a TE generator (TEG), which includes TE material with temperature-dependent properties. The influences of the geometric size, solar irradiation and cold side temperature on the hybrid system performance is discussed based on the simulation. Furthermore, the effective range of parameters is demonstrated using the image area method, and the change trend of the area with different parameters illustrates the constraint conditions of an efficient PV-TE hybrid system. These results provide a benchmark for efficient PV-TEG design.

A review on the development of photovoltaic/concentrated solar power (PV-CSP) hybrid systems

As an emerging technology, the photovoltaic/concentrated solar power (PV-CSP) hybrid technology is considered as one of the research focuses currently in solar energy field, due to various advantages compared with the PV-alone and CSP-alone technologies. Compared with the PV-alone system, the PV-CSP hybrid system can produce electricity with better power quality. While compared with the CSP-alone system, the cost of power production can be reduced. The overall generating efficiency will also be greatly improved if the PV component and the CSP component of the hybrid system are “compactly” hybridized by PV-topping or spectral beam splitting (SBS) technologies. The development of PV-CSP hybrid systems accelerated in recent years with the increase of maturity of PV and CSP technologies. This paper presents an exhaustive review on the state-of-the-art of the PV-CSP hybrid technologies, including the non-compact hybrid system, the PV-topping hybrid system, the SBS hybrid system, and the hybrid system combining SBS and PV-topping technologies. Recent progresses of the key technologies of the PV-CSP hybrid systems, such as high temperature solar cells, spectral beam filters, and high flux heat exchangers, are generally discussed. After that, the research status and the hybrid system performance are summarized from the literature to provide a global point of view on the PV-CSP hybrid technology. The advantages and limitations of the hybrid technology are also concluded according to the literature reviewed.

Studying the impact of language-independent and language-specific features on hybrid Arabic Person name recognition

In this paper, extensive experiments are conducted to study the impact of features of different categories, in isolation and gradually in an incremental manner, on Arabic Person name recognition. We present an integrated system that employs the rule-based approach with the machine learning (ML)-based approach in order to develop a consolidated hybrid system. Our feature space is comprised of language-independent and language-specific features. The explored features are naturally grouped under six categories: Person named entity tags predicted by the rule-based component, word-level features, POS features, morphological features, gazetteer features, and other contextual features. As decision tree algorithm has proved comparatively higher efficiency as a classifier in current state-of-the-art hybrid Named Entity Recognition for Arabic, it is adopted in this study as the ML technique utilized by the hybrid system. Therefore, the experiments are focused on two dimensions: the standard dataset used and the set of selected features. A number of standard datasets are used for the training and testing of the hybrid system, including ACE (2003---2004) and ANERcorp. The experimental analysis indicates that both language-independent and language-specific features play an important role in overcoming the challenges posed by Arabic language and have demonstrated critical impact on optimizing the performance of the hybrid system.

Removal of dissolved organic carbon and bromide by a hybrid MIEX-ultrafiltration system: Insight into the behaviour of organic fractions

Dissolved organic carbon (DOC) and bromide (Br−) are principal precursors in the formation of halogenated disinfection by-products resulting from chlorination of drinking water. Their effective removal from water represents, thus, one of the main challenges faced by drinking water treatment plants worldwide. The objective of this study was to evaluate the performance of a pilot-scale hybrid system based on the patented magnetic ion-exchange resin (MIEX) combined with ultrafiltration (UF) in the removal of DOC and Br− from water. Two different doses of MIEX (1mL/L and 3mL/L) were applied and compared. Samples of feed water, UF permeate and tank solution were regularly collected to assess the system performance in terms of removal of DOC and Br−. DOC was characterised by high-performance size-exclusion chromatography (HPSEC) and 3D-fluorescence excitation-emission matrix (FEEM) to identify which organic fractions were preferentially removed by the MIEX/UF process. Results demonstrated that the hybrid MIEX/UF system was able to remove DOC and Br− from water. The evolution and extent of these removals depended on the MIEX dose applied, with percentage removals clearly increasing when the MIEX dose was increased from 1mL/L to 3mL/L. MIEX exhibited higher affinity toward DOC than toward Br−. Saturation of MIEX toward Br− was achieved short after the start of the experiment, while removal of DOC persisted until the end of the experiment. Fractionation of DOC by HPSEC indicated that the highest molecular weight fraction was mainly removed by size-exclusion by the UF membrane, while lower molecular weight fractions seemed to be better removed by ion-exchange on the MIEX resin. FEEM analysis revealed a poor affinity of MIEX toward microbial by-products, whereas fulvic and humic acid-like material were the most retained by MIEX.